I have not ordered much from 4 into 1, but what I have, was utterly useless as a functioning part. Yeah, the 4 into 1 stuff is cheap, but that money was just thrown in the trash if you actually intend to ride your bike.
About the only good parts I've found from 4into1 are:
-Vesrah gasket kits (they are the same everywhere).
-The 4into1 spark advancer, using just the base and the cam, replacing the springs. Sometimes I have also used the weights, or just swapped the ones from the [bad] OEM advancer I was trying to fix up.
-NGK plug caps (but those might be vanishing?)
When 4into1 first appeared, they were the primary source of the WRONG head seal pucks that we all enjoyed [not].